Does ecology shape geographical parthenogenesis? Evidence from the facultatively parthenogenetic stick insect Megacrania batesii.

Closely related sexual and parthenogenetic species often show distinct distribution patterns, known as geographical parthenogenesis. Similar patterns, characterized by the existence of separate sexual and parthenogenetic populations across their natural range, can also be found in facultative parthenogens - species in which every female is capable of both sexual and parthenogenetic reproduction. The underlying mechanisms driving this phenomenon in nature remain unclear. Features of the habitat, such as differences in host-plant phenotypes or niche breadth, could favour sexual or asexual reproductive modes and thus help to explain geographical parthenogenesis in natural insect populations. Megacrania batesii is a facultatively parthenogenetic stick insect that displays geographical parthenogenesis in the wild. We aimed to explore whether sexual and parthenogenetic populations of M. batesii displayed niche differentiation or variations in niche breadth that could explain the separation of the two population types. To do this, we sampled host plants from across the range of M. batesii and quantified phenotypic traits that might affect palatability or accessibility for M. batesii, including leaf thickness, toughness, spike size and density, plant height, and chemical composition. We also quantified host-plant density, which could affect M. batesii dispersal. We found little evidence of phenotypic differences between host plants supporting sexual versus asexual M. batesii populations, and no difference in host-plant density or niche breadth between the two population types. Our results suggest that habitat parameters do not play a substantial role in shaping patterns of geographical parthenogenesis in wild populations of M. batesii. Instead, population sex ratio variation could result from interactions between the sexes or dispersal dynamics.

Trematode Diplostomum pseudospathaceum inducing differential immune gene expression in sexual and gynogenetic gibel carp (Carassius gibelio): parasites facilitating the coexistence of two reproductive forms of the invasive species.

Introduction: Parasite-mediated selection is considered one of the potential mechanisms contributing to the coexistence of asexual-sexual complexes. Gibel carp (Carassius gibelio), an invasive fish species in Europe, often forms populations composed of gynogenetic and sexual specimens. Methods: The experimental infection was induced in gynogenetic and sexual gibel carp using eye-fluke Diplostomum pseudospathaceum (Trematoda), and the transcriptome profile of the spleen as a major immune organ in fish was analyzed to reveal the differentially expressed immunity-associated genes related to D. pseudospathaceum infection differing between gynogenetic and sexual gibel carp. Results: High parasite infection was found in gynogenetic fish when compared to genetically diverse sexuals. Although metacercariae of D. pseudospathaceum are situated in an immune-privileged organ, our results show that eye trematodes may induce a host immune response. We found differential gene expression induced by eye-fluke infection, with various impacts on gynogenetic and sexual hosts, documenting for the majority of DEGs upregulation in sexuals, and downregulation in asexuals. Differences in gene regulation between gynogenetic and sexual gibel carp were evidenced in many immunity-associated genes. GO analyses revealed the importance of genes assigned to the GO terms: immune function, the Notch signaling pathway, MAP kinase tyrosine/threonine/phosphatase activity, and chemokine receptor activity. KEGG analyses revealed the importance of the genes involved in 12 immunity-associated pathways - specifically, FoxO signaling, adipocytokine signaling, TGF-beta signaling, apoptosis, Notch signaling, C-type lectin receptor signaling, efferocytosis, intestinal immune network for IgA production, insulin signaling, virion - human immunodeficiency virus, Toll-like receptor signaling, and phosphatidylinositol signaling system. Discussion: Our study indicates the limited potential of asexual fish to cope with higher parasite infection (likely a loss of capacity to induce an effective immune response) and highlights the important role of molecular mechanisms associated with immunity for the coexistence of gynogenetic and sexual gibel carp, potentially contributing to its invasiveness.

Functional characterization of BbEaf6 in Beauveria bassiana: Implications for fungal virulence and stress response.

The Eaf6 protein, a conserved component of the NuA4 and NuA3 complexes in yeast and MOZ/MORF complexes in humans, plays crucial roles in transcriptional activation, gene regulation, and cell cycle control. Despite its significance in other organisms, the functional role of Eaf6 in entomopathogenic fungi (EPF) remained unexplored. Here, we investigate the function of BbEaf6, the Eaf6 homolog in the entomopathogenic fungus Beauveria bassiana. We demonstrate that BbEaf6 is predominantly localized in nuclei, similar to its counterpart in other fungi. Deletion of BbEaf6 resulted in delayed conidiation, reduced conidial yield, and altered conidial properties. Transcriptomic analysis revealed dysregulation of the genes involved in asexual development and cell cycle progression in the ΔBbEaf6 mutant. Furthermore, the ΔBbEaf6 mutant exhibited decreased tolerance to various stresses, including ionic stress, cell wall perturbation, and DNA damage stress. Notably, the ΔBbEaf6 mutant displayed attenuated virulence in insect bioassays, accompanied by dysregulation of genes associated with cuticle penetration and haemocoel infection. Overall, our study elucidates the multifaceted role of BbEaf6 in stress response, development, and virulence in B. bassiana, providing valuable insights into the molecular mechanisms governing fungal pathogenesis and potential targets for pest management strategies.

Apomixis beyond trees in the Brazilian savanna: new insights from the orchid Zygopetalum mackayi.

n the Neotropics, the focus of apomictic studies predominantly centres on trees within the Brazilian savanna, characterized, mostly as sporophytic and facultative, associated with polyploidy and polyembryony. To enhance our understanding of the mechanisms governing apomixis and sexual reproduction in tropical herbaceous plants, we clarify the relationship between apomixis, chromosome counts, and polyembryony in the epiphytic orchid Zygopetalum mackayi, which forms a polyploid complex within rocky outcrops in both the Brazilian savanna and the Atlantic forest. To define embryo origins and describe megasporogenesis and megagametogenesis, we performed manual self-pollinations in first-day flowers of cultivated plants, considering all three cytotypes (2x, 3x, 4x) of this species. Flowers and fruits at different stages were collected to describe the development and morphology of ovules and seeds considering sexual and apomictic processes. As self-pollination treatments resulted in high fruit abortion in diploids, we also examined pollen tube development in aborted flowers and fruits to search for putative anomalies. Megasporogenesis and megagametogenesis occur regularly in all cytotypes. Apomixis is facultative and sporophytic, and associated with polyploid cytotypes, while diploid individuals exclusively engage in sexual reproduction. Polyembryony is caused mainly by the production of adventitious embryos from nucellar cells of triploids and tetraploids, but also by the development of multiple archesporia in all cytotypes. Like other apomictic angiosperms within the Brazilian savanna, our findings demonstrate that apomixis in Z. mackayi relies on pollinators for seed production. We also consider the ecological implications of these apomictic patterns in Z. mackayi within the context of habitat loss and its dependence on pollinators.

Evidence for the production of asexual resting cysts in a free-living species of Symbiodiniaceae (Dinophyceae).

Coral reef ecosystems are the most productive and biodiverse marine ecosystems, with their productivity levels highly dependent on the symbiotic dinoflagellates belonging to the family Symbiodiniaceae. As a unique life history strategy, resting cyst production is of great significance in the ecology of many dinoflagellate species, those HABs-causing species in particular, however, there has been no confirmative evidence for the resting cyst production in any species of the family Symbiodiniaceae. Based on morphological and life history observations of cultures in the laboratory and morpho-molecular detections of cysts from the marine sediments via fluorescence in situ hybridization (FISH), cyst photography, and subsequent singe-cyst PCR sequencing, here we provide evidences for the asexual production of resting cysts by Effrenium voratum, the free-living, red tide-forming, and the type species of the genus Effrenium in Symbiodiniaceae. The evidences from the marine sediments were obtained through a sequential detections: Firstly, E. voratum amplicon sequence variants (ASVs) were detected in the cyst assemblages that were concentrated with the sodium polytungstate (SPT) method from the sediments collected from different regions of China Seas by high-throughput next generation sequencing (NGS); Secondly, the presence of E. voratum in the sediments was detected by PCR using the species-specific primers for the DNA directly extracted from sediment; Thirdly, E. voratum cysts were confirmed by a combined approach of FISH using the species-specific probes, light microscopic (LM) photography of the FISH-positive cysts, and a subsequent single-cyst PCR sequencing for the FISH-positive and photographed cysts. The evidences from the laboratory-reared clonal cultures of E. voratum include that: 1) numerous cysts formed in the two clonal cultures and exhibited a spherical shape, a smooth surface, absence of ornaments, and a large red accumulation body; 2) cysts could maintain morphologically intact for a storage of two weeks to six months at 4 °C in darkness and of which 76-92 % successfully germinated through an internal development processes within a time period of 3-21 days after being transferred back to the normal culturing conditions; 3) two or four germlings were released from each cyst through the cryptopylic archeopyle in all cysts with continuous observations of germination processes; and 4) while neither sexual mating of gametes nor planozygote (cells with two longitudinal flagella) were observed, the haploidy of cysts was proven with flow cytometric measurements and direct LM measurements of fluorescence from cells stained with either propidium iodide (PI) or DAPI, which together suggest that the cysts were formed asexually. All evidences led to a conclusion that E. voratum is capable of producing asexual resting cysts, although its sexuality cannot be completely excluded, which guarantees a more intensive investigation. This work fills a gap in the knowledge about the life cycle, particularly the potential of resting cyst formation, of the species in Symbiodiniaceae, a group of dinoflagellates having unique life forms and vital significance in the ecology of coral reefs, and may provide novel insights into understanding the recovery mechanisms of coral reefs destructed by the global climate change and suggest various forms of resting cysts in the cyst assemblages of dinoflagellates observed in the field sediments, including HABs-causing species.

Two enzymes contribute to citrate production in the mitochondrion of Toxoplasma gondii.

Citrate synthase catalyzes the first and the rate-limiting reaction of the tricarboxylic acid (TCA) cycle, producing citrate from the condensation of oxaloacetate and acetyl-coenzyme A. The parasitic protozoan Toxoplasma gondii has full TCA cycle activity, but its physiological roles remain poorly understood. In this study, we identified three proteins with predicted citrate synthase (CS) activities two of which were localized in the mitochondrion, including the 2-methylcitrate synthase (PrpC) that was thought to be involved in the 2-methylcitrate cycle, an alternative pathway for propionyl-CoA detoxification. Further analyses of the two mitochondrial enzymes showed that both had citrate synthase activity, but the catalytic efficiency of CS1 was much higher than that of PrpC. Consistently, the deletion of CS1 resulted in a significantly reduced flux of glucose-derived carbons into TCA cycle intermediates, leading to decreased parasite growth. In contrast, disruption of PrpC had little effect. On the other hand, simultaneous disruption of both CS1 and PrpC resulted in more severe metabolic changes and growth defects than a single deletion of either gene, suggesting that PrpC does contribute to citrate production under physiological conditions. Interestingly, deleting Δcs1 and Δprpc individually or in combination only mildly or negligibly affected the virulence of parasites in mice, suggesting that both enzymes are dispensable in vivo. The dispensability of CS1 and PrpC suggests that either the TCA cycle is not essential for the asexual reproduction of tachyzoites or there are other routes of citrate supply in the parasite mitochondrion.

Gene expression response under thermal stress in two Hawaiian corals is dominated by ploidy and genotype.

Transcriptome data are frequently used to investigate coral bleaching; however, the factors controlling gene expression in natural populations of these species are poorly understood. We studied two corals, Montipora capitata and Pocillopora acuta, that inhabit the sheltered Kane'ohe Bay, Hawai'i. M. capitata colonies in the bay are outbreeding diploids, whereas P. acuta is a mixture of clonal diploids and triploids. Populations were sampled from six reefs and subjected to either control (no stress), thermal stress, pH stress, or combined pH and thermal stress treatments. RNA-seq data were generated to test two competing hypotheses: (1) gene expression is largely independent of genotype, reflecting a shared treatment-driven response (TDE) or, (2) genotype dominates gene expression, regardless of treatment (GDE). Our results strongly support the GDE model, even under severe stress. We suggest that post-transcriptional processes (e.g., control of translation, protein turnover) modify the signal from the transcriptome, and may underlie the observed differences in coral bleaching sensitivity via the downstream proteome and metabolome.

Two novel members of Onygenales, Keratinophyton kautmanovae and K. keniense spp. nov. from soil.

Two new Keratinophyton species, K. kautmanovae sp. nov. and K. keniense sp. nov., isolated from soil samples originating from two different geographical and environmental locations (Africa and Europe) are described and illustrated. Phylogenetically informative sequences obtained from the internal transcribed spacer (ITS) region and the nuclear large subunit (LSU) rDNA, as well as their unique phenotype, fully support novelty of these two fungi for this genus. Based on ITS and LSU combined phylogeny, both taxa are resolved in a cluster with eight accepted species, including K. alvearium, K. chongqingense, K. hubeiense, K. durum, K. lemmensii, K. siglerae, K. submersum, and K. sichuanense. The new taxon, K. kautmanovae, is characterized by clavate, smooth to coarsely verrucose conidia, absence of arthroconidia, slow growth at 25 °C, and no growth at 30 °C, while K. keniense is morphologically unique with a high diversity of conidial shapes (clavate, filiform, globose, cymbiform and rhomboid). Both species are described based on their asexual, a chrysosporium-like morph. While the majority of hitherto described Keratinophyton taxa came from Europe, India and China, the new species K. keniense represents the first reported taxonomic novelty for this genus from Africa.

Depressive symptoms among individuals identifying as asexual: a cross-sectional study.

Although asexuality became a growing research subject over the last decade, data on the mental health of individuals identifying as asexual is still rare. The key objective of the present study was to examine depressive symptoms among individuals identifying as asexual. Data of LGBTQIA+ (Lesbian, Gay, Bi-sexual, Trans*, Queer, Inter*, Asexual and/or + indicating others within the community) and cisgender heterosexual individuals was collected through an online survey during the COVID-19 lockdowns in Germany. The survey included questions about sexual and gender identity, depressive symptoms, and asexual identity. An analysis of N = 6601 participants was conducted. A total of n = 445 individuals identified as asexual. Regression results indicated identifying as asexual being significantly associated with higher depressive symptoms. Results suggest that individuals identifying as asexual represent a vulnerable group within the group of sexual minorities, one that fundamentally requires special psychosocial support, especially in times of pandemics.

Reproduction-associated pathways in females of gibel carp (Carassius gibelio) shed light on the molecular mechanisms of the coexistence of asexual and sexual reproduction.

Gibel carp (Carassius gibelio) is a cyprinid fish that originated in eastern Eurasia and is considered as invasive in European freshwater ecosystems. The populations of gibel carp in Europe are mostly composed of asexually reproducing triploid females (i.e., reproducing by gynogenesis) and sexually reproducing diploid females and males. Although some cases of coexisting sexual and asexual reproductive forms are known in vertebrates, the molecular mechanisms maintaining such coexistence are still in question. Both reproduction modes are supposed to exhibit evolutionary and ecological advantages and disadvantages. To better understand the coexistence of these two reproduction strategies, we performed transcriptome profile analysis of gonad tissues (ovaries) and studied the differentially expressed reproduction-associated genes in sexual and asexual females. We used high-throughput RNA sequencing to generate transcriptomic profiles of gonadal tissues of triploid asexual females and males, diploid sexual males and females of gibel carp, as well as diploid individuals from two closely-related species, C. auratus and Cyprinus carpio. Using SNP clustering, we showed the close similarity of C. gibelio and C. auratus with a basal position of C. carpio to both Carassius species. Using transcriptome profile analyses, we showed that many genes and pathways are involved in both gynogenetic and sexual reproduction in C. gibelio; however, we also found that 1500 genes, including 100 genes involved in cell cycle control, meiosis, oogenesis, embryogenesis, fertilization, steroid hormone signaling, and biosynthesis were differently expressed in the ovaries of asexual and sexual females. We suggest that the overall downregulation of reproduction-associated pathways in asexual females, and their maintenance in sexual ones, allows the populations of C. gibelio to combine the evolutionary and ecological advantages of the two reproductive strategies. However, we showed that many sexual-reproduction-related genes are maintained and expressed in asexual females, suggesting that gynogenetic gibel carp retains the genetic toolkits for meiosis and sexual reproduction. These findings shed new light on the evolution of this asexual and sexual complex.

Ectodermal origin and tissue dedifferentiation in the podocyst production by the polyps of the Asian moon jelly (Aurelia coerulea).

The histological origin of podocysts in scyphozoans has long been undetermined, with uncertainty whether they arise from mesenchymal amoebocytes or stalk and pedal disc ectoderm in polyps. Histological investigation on the pedal disc was difficult due to the settlement of polyps on hard substrates. In this study, we investigated the histological characteristics of polyps during podocyst production in Asian moon jelly (Aurelia coerulea) with utilizing those attached on thin polystyrene substrates. Fine histological features of the pedal disc became possible after the substrates were decomposed during histological processing. Our findings unequivocally demonstrate that the cell mass of podocysts originates from the ectoderm of the pedal disc and the stalk without the involvement of amoebocytes in the mesoglea. Preceding the podocyst formation, the pedal disc undergoes enlargement facilitated by the elongated stalk ectodermal cells, which attach to a substrate. Subsequently, the pedal disc ectoderm give rise to the primary podocyst cells with accumulating nutrient granules in the cytoplasm and forming the cyst capsule cooperatively with the invaginated pedal disc ectoderm. Direct transformation from the ectodermal cells to podocyst cells suggests that podocyst formation involves tissue dedifferentiation. Throughout the period of podocyst production, the gastrodermis of polyps is physically separated from the ectoderm by the mesoglea and shows no histological changes, and no amoebocytes appear in the mesoglea. These histological properties are totally different from those in other modes of asexual reproduction, which incorporate the endoderm of polyps, suggesting the developmental and evolutionary differences between these asexual reproductions and podocyst production in Scyphozoa.

Multiple hybridization events and repeated evolution of homoeologue expression bias in parthenogenetic, polyploid New Zealand stick insects.

During hybrid speciation, homoeologues combine in a single genome. Homoeologue expression bias (HEB) occurs when one homoeologue has higher gene expression than another. HEB has been well characterized in plants but rarely investigated in animals, especially invertebrates. Consequently, we have little idea as to the role that HEB plays in allopolyploid invertebrate genomes. If HEB is constrained by features of the parental genomes, then we predict repeated evolution of similar HEB patterns among hybrid genomes formed from the same parental lineages. To address this, we reconstructed the history of hybridization between the New Zealand stick insect genera Acanthoxyla and Clitarchus using a high-quality genome assembly from Clitarchus hookeri to call variants and phase alleles. These analyses revealed the formation of three independent diploid and triploid hybrid lineages between these genera. RNA sequencing revealed a similar magnitude and direction of HEB among these hybrid lineages, and we observed that many enriched functions and pathways were also shared among lineages, consistent with repeated evolution due to parental genome constraints. In most hybrid lineages, a slight majority of the genes involved in mitochondrial function showed HEB towards the maternal homoeologues, consistent with only weak effects of mitonuclear incompatibility. We also observed a proteasome functional enrichment in most lineages and hypothesize this may result from the need to maintain proteostasis in hybrid genomes. Reference bias was a pervasive problem, and we caution against relying on HEB estimates from a single parental reference genome.

Comprehensive Insights into the Remarkable Function and Regulatory Mechanism of FluG during Asexual Development in Beauveria bassiana.

Asexual development is the main propagation and transmission mode of Beauveria bassiana and the basis of its pathogenicity. The regulation mechanism of conidiation and the key gene resources for utilization are key links to improving the conidia yield and quality of Beauveria bassiana. Their clarification may promote the industrialization of fungal pesticides. Here, we compared the regulation of morphology, resistance to external stress, virulence, and nutrient utilization capacity between the upstream developmental regulatory gene fluG and the key genes brlA, abaA, and wetA in the central growth and development pathway. The results showed that the ΔbrlA and ΔabaA mutants completely lost the capacity to conidiate and that the ΔwetA mutant had seriously reduced conidiation capacity. Although the deletion of fluG did not reduce the conidiation ability as much as deletions of brlA, abaA, and wetA, it significantly reduced the fungal response to external stress, virulence, and nutrient utilization, while the deletion of the three other genes had little effect. Via transcriptome analysis and screening the yeast nuclear system library, we found that the differentially expressed genes in the ΔfluG mutants were concentrated in the signaling pathways of ABC transporters, propionate metabolism, tryptophan metabolism, DNA replication, mismatch repair, and fatty acid metabolism. FluG directly acted on 40 proteins that were involved in various signaling pathways such as metabolism, oxidative stress, and cell homeostasis. The analysis indicated that the regulatory function of fluG was mainly involved in DNA replication, cell homeostasis, fungal growth and metabolism, and the response to external stress. Our results revealed the biological function of fluG in asexual development and the responses to several environmental stresses as well as its influence on the asexual development regulatory network in B. bassiana.

Cla4A, a Novel Regulator of Gene Expression Networks Required for Asexual and Insect-Pathogenic Lifecycles of Beauveria bassiana.

Cla4, an orthologous p21-activated kinase crucial for non-entomopathogenic fungal lifestyles, has two paralogs (Cla4A/B) functionally unknown in hypocrealean entomopathogens. Here, we report a regulatory role of Cla4A in gene expression networks of Beauveria bassiana required for asexual and entomopathogenic lifecycles while Cla4B is functionally redundant. The deletion of cla4A resulted in severe growth defects, reduced stress tolerance, delayed conidiation, altered conidiation mode, impaired conidial quality, and abolished pathogenicity through cuticular penetration, contrasting with no phenotype affected by cla4B deletion. In ∆cla4A, 5288 dysregulated genes were associated with phenotypic defects, which were restored by targeted gene complementation. Among those, 3699 genes were downregulated, including more than 1300 abolished at the transcriptomic level. Hundreds of those downregulated genes were involved in the regulation of transcription, translation, and post-translational modifications and the organization and function of the nuclear chromosome, chromatin, and protein-DNA complex. DNA-binding elements in promoter regions of 130 dysregulated genes were predicted to be targeted by Cla4A domains. Samples of purified Cla4A extract were proven to bind promoter DNAs of 12 predicted genes involved in multiple stress-responsive pathways. Therefore, Cla4A acts as a novel regulator of genomic expression and stability and mediates gene expression networks required for insect-pathogenic fungal adaptations to the host and environment.

Three new species of Neohelicomyces (Tubeufiales, Tubeufiaceae) from freshwater and terrestrial habitats in China.

Neohelicomyces species are a group of helicosporous hyphomycetes with the potential to produce secondary metabolites. During our investigation of helicosporous fungi, six collections were isolated from both terrestrial and freshwater habitats in Guizhou Province, China. Based on multigene phylogenetic analysis (ITS, LSU, tef1α and rpb2), coupled with morphological data, three new Neohelicomyces species, viz. N.guizhouensis, N.helicosporus and N.hydei were established. A list of accepted Neohelicomyces species with molecular data was provided. The strain of Neohelicomycespallidus (UAMH 10535) was synonymised under N.denticulatus based on molecular data.

Hyphal editing of the conserved premature stop codon in CHE1 is stimulated by oxidative stress in Fusarium graminearum.

Although genome-wide A-to-I editing mediated by adenosine-deaminase-acting-on-tRNA (ADAT) occurs during sexual reproduction in the presence of stage-specific cofactors, RNA editing is not known to occur during vegetative growth in filamentous fungi. Here we identified 33 A-to-I RNA editing events in vegetative hyphae of Fusarium graminearum and functionally characterized one conserved hyphal-editing site. Similar to ADAT-mediated editing during sexual reproduction, majority of hyphal-editing sites are in coding sequences and nonsynonymous, and have strong preference for U at -1 position and hairpin loops. Editing at TA437G, one of the hyphal-specific editing sites, is a premature stop codon correction (PSC) event that enables CHE1 gene to encode a full-length zinc fingertranscription factor. Manual annotations showed that this PSC site is conserved in CHE1 orthologs from closely-related Fusarium species. Whereas the che1 deletion and CHE1TAA (G438 to A) mutants had no detectable phenotype, the CHE1TGG (A437 to G) mutant was defective in hyphal growth, conidiation, sexual reproduction, and plant infection. However, the CHE1TGG mutant was increased in tolerance against oxidative stress and editing of TA437G in CHE1 was stimulated by H2O2 treatment in F. graminearum. These results indicate that fixation of the premature stop codon in CHE1 has a fitness cost on normal hyphal growth and reproduction but provides a benefit to tolerance against oxidative stress. Taken together, A-to-I editing events, although rare (not genome-wide), occur during vegetative growth and editing in CHE1 plays a role in response to oxidative stress in F. graminearum and likely in other fungal pathogens.

Virulence is associated with daily rhythms in the within-host replication of the malaria parasite Plasmodium chabaudi.

Most malaria (Plasmodium spp.) parasite species undergo asexual replication synchronously within the red blood cells of their vertebrate host. Rhythmicity in this intraerythrocytic developmental cycle (IDC) enables parasites to maximise exploitation of the host and align transmission activities with the time of day that mosquito vectors blood feed. The IDC is also responsible for the major pathologies associated with malaria, and plasticity in the parasite's rhythm can confer tolerance to antimalarial drugs. Both the severity of infection (virulence) and synchrony of the IDC vary across species and between genotypes of Plasmodium; however, this variation is poorly understood. The theory predicts that virulence and IDC synchrony are negatively correlated, and we tested this hypothesis using two closely related genotypes of the rodent malaria model Plasmodium chabaudi that differ markedly in virulence. We also test the predictions that, in response to perturbations to the timing (phase) of the IDC schedule relative to the phase of host rhythms (misalignment), the virulent parasite genotype recovers the correct phase relationship faster, incurs less fitness losses and so hosts benefit less from misalignment when infected with a virulent genotype. Our predictions are partially supported by results suggesting that the virulent parasite genotype is less synchronous in some circumstances and recovers faster from misalignment. While hosts were less anaemic when infected by misaligned parasites, the extent of this benefit did not depend on parasite virulence. Overall, our results suggest that interventions to perturb the alignment between the IDC schedule, and host rhythms and increase synchrony between parasites within each IDC, could alleviate disease symptoms. However, virulent parasites, which are better at withstanding conventional antimalarial treatment, would also be intrinsically better able to tolerate such interventions.

IgG and IgM responses to the Plasmodium falciparum asexual stage antigens reflect respectively protection against malaria during pregnancy and infanthood.

BACKGROUND: Plasmodium falciparum malaria is a public health issue mostly seen in tropical countries. Until now, there is no effective malaria vaccine against antigens specific to the blood-stage of P. falciparum infection. Because the pathogenesis of malarial disease results from blood-stage infection, it is essential to identify the most promising blood-stage vaccine candidate antigens under natural exposure to malaria infection. METHODS: A cohort of 400 pregnant women and their infants was implemented in South Benin. An active and passive protocol of malaria surveillance was established during pregnancy and infancy to precisely ascertain malaria infections during the follow-up. Twenty-eight antibody (Ab) responses specific to seven malaria candidate vaccine antigens were repeatedly quantified during pregnancy (3 time points) and infancy (6 time points) in order to study the Ab kinetics and their protective role. Abs were quantified by ELISA and logistic, linear and cox-proportional hazard model were performed to analyse the associations between Ab responses and protection against malaria in mothers and infants, taking into account socio-economic factors and for infants an environmental risk of exposure. RESULTS: The levels of IgM against MSP1, MSP2 and MSP3 showed an early protective response against the onset of symptomatic malaria infections starting from the 18th month of life, whereas no association was found for IgG responses during infancy. In women, some IgG responses tend to be associated with a protection against malaria risk along pregnancy and at delivery, among them IgG3 against GLURP-R0 and IgG2 against MSP1. CONCLUSION: The main finding suggests that IgM should be considered in vaccine designs during infanthood. Investigation of the functional role played by IgM in malaria protection needs further attention.

Comparative Genomics of Sex, Chromosomes, and Sex Chromosomes in Caenorhabditis elegans and Other Nematodes.

The nematode phylum has evolved a remarkable diversity of reproductive modes, including the repeated emergence of asexuality and hermaphroditism across divergent clades. The species-richness and small genome size of nematodes make them ideal systems for investigating the genome-wide causes and consequences of such major transitions. The availability of functional annotations for most Caenorhabditis elegans genes further allows the linking of patterns of gene content evolution with biological processes. Such gene-centric studies were recently complemented by investigations of chromosome evolution that made use of the first chromosome-scale genome assemblies outside the Caenorhabditis genus. This review highlights recent comparative genomic studies of reproductive mode evolution addressing the hybrid origin of asexuality and the parallel gene loss following the emergence of hermaphroditism. It further summarizes ongoing efforts to characterize ancient linkage blocks called Nigon elements, which form central units of chromosome evolution. Fusions between Nigon elements have been demonstrated to impact recombination and speciation. Finally, multiple recent fusions between autosomal and the sex-linked Nigon element reveal insights into the dynamic evolution of sex chromosomes across various timescales.

The Arf-GAPs, AoAge1 and AoAge2, regulate diverse cellular processes, conidiation, trap formation, and secondary metabolism in Arthrobotrys oligospora.

Guanine nucleotide-binding proteins of the ADP ribosylation factor (Arf) family and their activating proteins (Arf-GAPs) are essential for diverse biological processes. Here, two homologous Arf-GAPs, Age1 (AoAge1) and Age2 (AoAge2), were identified in the widespread nematode-trapping fungus Arthrobotrys oligospora. Our results demonstrated that AoAge1, especially AoAge2, played crucial roles in mycelial growth, sporulation, trap production, stress response, mitochondrial activity, DNA damage, endocytosis, reactive oxygen species production, and autophagy. Notably, transcriptome data revealed that approximately 62.7% of the genes were directly or indirectly regulated by AoAge2, and dysregulated genes in Aoage2 deletion were enriched in metabolism, ribosome biogenesis, secondary metabolite biosynthesis, and autophagy. Furthermore, Aoage2 inactivation caused a substantial reduction in several compounds compared to the wild-type strain. Based on these results, a regulatory network for AoAge1 and AoAge2 was proposed and verified using a yeast two-hybrid assay. Based on our findings, AoAge1 and AoAge2 are essential for vegetative growth and mycelial development. Specifically, AoAge2 is required for sporulation and trapping morphogenesis. Our results demonstrated the critical functions of AoAge1 and AoAge2 in mycelial growth, diverse cellular processes, and pathogenicity, offering deep insights into the functions and regulatory mechanisms of Arf-GAPs in nematode-trapping fungi.